Need to run existing cable underground

I'm going to be building a garage in my back yard and I need to have the existing overhead wire that currently feeds my service buried. Where I plan on putting the garage will interfere with the construction of it. There is also a power wire right above the Xfinity wire that will also be run underground as well. I will have a trench dug for the power line. I'm hoping to be able to bury both wires at the same time if possible. I've called customer service twice and explained what I need done and within minutes they close my ticket.